Infrared laser spectrum of the fundamental band of the boron monoxide free radical

The infrared diode laser absorption spectrum of the fundamental band of the boron monoxide (BO) radical in its ground 2Σ+ state has been observed. The source of the radical was the reaction of BCl3 with O3P in the absence of molecular oxygen. 15 lines of 11BO and three lines of 10BO have been measured. The 10BO lines show a small, partially resolved, doublet structure of about 0.01 cm−1 which is not present in the 11BO species. This is attributed to the complex hyperfine pattern expected for the 10B (I=3) nucleus. The band origins are 1861.92465(48) and 1915.30554(16) cm−1, respectively. Combining the diode laser value of B1=1.756829(11) cm−1 with the microwave determination of B0 leads to a value of re=1.204068(7) Å for 11BO.